Method and apparatus for polishing control with signal peak analysis

The apparatus for polishing control with signal peak analysis consists of two major units: a polishing machine and a polishing process control and monitoring system which has sensors for sensing changes on the surface and/or inside the object during polishing. In response to the above changes the sensors generate operating data signals. The control and monitoring system, which also contains a signal conditioning unit and a control unit, amplifies the operating data signals and sends them to a signal analyzer, which determines average values and peaks of the conditioned signals. The analyzer also determines a ratio of the peak signal values to an average signal values and compares the obtained ratio with a preliminarily determined reference value optimized with regard to the specific CMP process carried out on the polishing machine. When the measured signal ratio reflects abnormal conditions, polishing conditions are adjusted back to normal by means of a control signal generated on the basis of the aforementioned ratio. The apparatus of the invention also provides quantitative evaluation of changes in the CMP process and automatic control of the CMP process in a manner that optimizes the process and prevents occurrence of defects that might be caused by the controlled process.